Iodine is an essential mineral that our body needs to make thyroid hormones. These hormones control our metabolism, growth, and development. When we don't get enough iodine, our body can't produce these hormones, leading to conditions like goiter (an enlarged thyroid gland) and hypothyroidism (underactive thyroid).

Globally, it's a significant issue, with an estimated 35-45% of the world's population affected by iodine deficiency. Recent studies show that even in developed nations like the United States, the United Kingdom, and Australia, iodine intake is declining. This is especially concerning for women of reproductive age in the U.S., who are at a higher risk of deficiency. However, you should be aware that excess iodine also contributes to thyroid imbalances.

What Causes Iodine Deficiency?

Several factors contribute to the drop in iodine intake:

• Dietary Changes: People are eating fewer foods naturally rich in iodine.
• Food Preparation: The shift in how we prepare and process food can affect its iodine content.
• Agricultural Practices: The iodine content in soil has been depleted in many areas, particularly non-coastal regions, which means the crops grown there contain less iodine.

The most common reason for a personal deficiency is simply avoiding foods that are good sources of iodine, such as dairy products, eggs, fish, and iodized salt. Also, eating a lot of uncooked cruciferous vegetables like broccoli and cabbage can interfere with how the thyroid gland absorbs iodine.

How Iodine is Measured and Labeled

The U.S. Food and Drug Administration (FDA) has specific rules for food labeling. While food producers don't have to list the amount of naturally occurring iodine, they must include the percentage of the Daily Value (DV) if the product is fortified with iodine. The Recommended Dietary Allowance (RDA) for adults is 150 micrograms (mcg).

Because about 90% of the iodine we consume is excreted in our urine, doctors can measure the urinary iodine concentration to get a good idea of a person's recent iodine intake. This makes it a very useful tool for assessing iodine status. I test patients’ urinary iodine levels if they have thyroid conditions or have restricted diets such as vegan.

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Reference

Hatch-McChesney, A., & Lieberman, H. R. (2022). Iodine and iodine deficiency: A comprehensive review of a re-emerging issue. Nutrients, 14(17), Article 3474. https://doi.org/10.3390/nu14173474 

Want to learn more? Read our recent article: The Perils of Excessive Iodine Supplementation